Solid gold-nickel alloy nanoparticles and production method therof

ABSTRACT

The purpose of the present invention is to provide novel solid gold-nickel alloy nanoparticles and a production method thereof. Provided are solid gold-nickel alloy nanoparticles having a particle diameter of 500 nm or less. In particular, gold-nickel alloy nanoparticle are provided in which the concentration of nickel in the gold-nickel alloy is 2.0-92.7 wt %, and the main component is a gold-nickel alloy in which gold and nickel are in a nano-level fine mixed state. The gold-nickel alloy particles have as the main component a substitutional solid solution of gold and nickel. These gold-nickel alloy particles are optimally formed by mixing and discharging gold ions, and a substance having reducing characteristics in the thin film fluid occurring between processing surfaces which are arranged facing each other, which can move towards and away from each other, and at least one of which rotates relative to the other.

TECHNICAL FIELD

The present invention relates to solid gold-nickel alloy nanoparticlesand production method thereof.

In recent years, a gold-nickel alloy particle is receiving an attentionas a material such as, for example, a magnetic sensor, an electrodematerial, a capacitor, a catalyst, and a contact material. There is apossibility that characteristics thereof may be controlled by the ratioof gold and nickel in the gold-nickel alloy particle; and for example,it is known that even the gold-nickel alloy in the state wherein goldand nickel are not homogeneously mixed cannot only express performancesas a highly reliable electric contact material such as a connector, asmall relay, and a printed circuit board, these being used as a part ofan electronic part, and but also improve performances such as heatresistance, abrasion resistance, and catalytic performance, as comparedwith a gold single body. Because of these, the gold-nickel alloy is amaterial that is wanted in a wide range of an industrial field. However,similarly to a silver-copper alloy, generally the gold-nickel alloyforms a eutectic body so that it is difficult to form a solid solutionof homogeneously mixed gold and nickel. Therefore, in many cases, theexpected characteristics mentioned above as the gold-nickel alloy arenot fully realized. Moreover, the gold-nickel alloy is expected not onlyto further improve the existing characteristics but also to expressnovel characteristics by making it a nanoparticle; and thus, agold-nickel alloy nanoparticle is eagerly wanted.

As discussed above, in a solid alloy which contains gold and nickel,gold and nickel can exist in various forms; and it is shown that in anequilibrium diagram thereof, there is a specific region in which goldand nickel forms, for example, a eutectic body thereof, whereby they donot mix with each other and there is a solid phase in which they areeccentrically located. In such a specific region, gold and nickel whichconstitute the alloy thereof show an eccentrically located state inwhich the composition ratio of the entire alloy of gold and nickel islargely different from the composition ratio of the same within anextremely small area with a nanometer level; and as a result, in manycases, the characteristics expected as the alloy thereof are not fullyrealized.

As to a production method of the gold-nickel alloy particle, a powdermetallurgy method has been generally used; and in addition, as the othermethods, there are such methods as a liquid phase reduction method asdescribed in Patent Document 1, an atomizing method as described inPatent Document 2, and so forth. However, there has been no report yetwith regard to a gold-nickel alloy in which gold and nickel are mixedhomogeneously, especially with regard to a gold-nickel alloynanoparticle and a method for proving the same. Other than thesemethods, there is a method in which metal gold and metal nickel arerapidly cooled from the state of the solid solution thereof at hightemperature thereby obtaining a solid solution of a gold-nickel alloyparticle; however, this method tends to make the obtained gold-nickelalloy particle inhomogeneous, and in addition, this requires largeenergy, so that there are problems of a natural tendency to a highproduction cost and so forth.

In Patent Document 3 filed by the applicant of the present invention, amethod for producing a microparticle was provided. However, analysis ofthe particle obtained by using this disclosed method showed that it wasan inhomogeneous gold-nickel alloy particle. Therefore, a gold-nickelalloy nanoparticle, especially a gold-nickel alloy nanoparticle that isa homogeneous solid solution, as well as a method for producing thesame, has been eagerly wanted.

In Patent Document 4, which is filed by the present applicant, theproducing method of the silver-copper alloy particle is disclosed;however, analysis of the particle obtained by the producing methodthereof shown by Example reveals that this particle is the silver-copperalloy particle formed of the eutectic body or mixture of single bodiesof silver and copper. Accordingly, there has been no disclosure as tothe silver-copper alloy substantially not containing the eutectic body,especially as to the solid solution type silver-copper alloy.

The apparatus shown in Patent Document 3 and 4 is the one in which fineparticles are separated in a thin film fluid formed between at least twoprocessing surfaces which are disposed in a position they are faced witheach other so as to be able to approach to and separate from each other,at least one of which rotates relative to the other; and this apparatusis expected to be actively utilized in production of the particlesespecially with the size in the level of nanometers. Inventors of thepresent invention tried to produce various nanoparticles by using thisapparatus; however, all the relationships between the separation andreaction conditions and the results thereof have not been clarified yet.

Specifically, although it is not the solid gold-nickel alloynanoparticle, in a solid metal alloy particles, it was confirmed that inthe platinum-palladium alloy, the analysis result of the TEM-EDS of onepoint thereof was almost identical to the ICP analysis result thereof,wherein, the platinum-palladium alloy was said to be an all proportionalsolid solution metal, in spite that there is a tendency of phaseseparation at low temperature. On the other hand, as to a silver-copperalloy, only the silver-copper alloy particle in the state of a eutecticbody thereof or of the mixture of a silver single body and a coppersingle body could be obtained.

More specifically, obtained therein were the silver-copper alloyparticles that are similar to those shown in FIG. 14 to FIG. 16. In FIG.14(A) the STEM-HAADF picture thereof is shown; in FIG. 14(B) the EELSmapping result (Ag) thereof is shown; and in FIG. 14(C) the EELS mappingresult (Cu) thereof is shown. Results of FIG. 14 were obtained by usingthe energy dispersive X-ray analyzer Centurio (manufactured by JEOLLtd.) and by the atomic resolution analytical electron microscopeJEM-ARM 200F (manufactured by JEOL Ltd.) with the acceleration voltageof 200.0 kV and the magnification of 6000000. In FIG. 15(A) theSTEM-HAADF picture thereof is shown; in FIG. 15(B) the STEM mappingresult (Ag) thereof is shown; and in FIG. 15(C) the STEM mapping result(Cu) thereof is shown. Results of FIG. 15 were obtained by using the Cscorrector-equipped super high resolution STEM analyzer HD-2700 (equippedwith EDX) (manufactured by Hitachi High-Technologies Corp.) with theacceleration voltage of 200.0 kV and the magnification of 2200000. InFIG. 16(A) the STEM-HAADF picture thereof is shown; in FIG. 16(B) theSTEM mapping result (Ag) thereof is shown; and in FIG. 16(C) the STEMmapping result (Cu) thereof is shown. Results of FIG. 16 were obtainedby using the Cs corrector-equipped super high resolution STEM analyzerHD-2700 (equipped with EDX) (manufactured by Hitachi High-TechnologiesCorp.) with the acceleration voltage of 80.0 kV and the magnification of2000000.

In the silver-copper alloy particle in FIG. 14, copper is present incenter of the particle (core), silver is present around it (shell), andcopper is present on surface of the silver-copper alloy particle(average particle diameter of about 20 nm). From FIGS. 14 (B) and (C),it can be seen that there are some places where silver or copper is notpresent, namely, there are some places where 100% of silver is presentor 100% copper is present. The silver-copper alloy particle in FIG. 15is the silver-copper alloy particle (average particle diameter of about15 nm) in which silver and copper are eccentrically located in the sameparticle. Especially from (C), it can be seen that there is a placewhere copper is not present, that is, there is a place where 100% silveris present.

The silver-copper alloy particle in FIG. 16 is the silver-copper alloyparticle (average particle diameter of about 15 nm) comprising silver inhalf of it, namely, 100% silver being present therein, and copper in theother half, namely, 100% copper being present therein in the sameparticle.

FIG. 17 shows the silver-antimony alloy particle; and in FIG. 17(A) theSTEM-HAADF picture thereof is shown; in (B) the STEM mapping result (Ag)thereof is shown; and in (C) the STEM mapping result (Sb) thereof isshown. These were obtained by using the energy dispersive X-ray analyzerCenturio (manufactured by JEOL Ltd.) and by the atomic resolutionanalytical electron microscope JEM-ARM 200F (manufactured by JEOL Ltd.)with the acceleration voltage of 200.0 kV and the magnification of6000000.

In this silver-antimony alloy particle (particle diameter of about 20nm), silver particles having the size of 2 to 5 nm are present in thesame particle, wherein there is a place where 100% of antimony ispresent between silver particles by the EDS analysis without any silverpresent.

PRIOR ART DOCUMENTS Patent Document Patent Document 1: Japanese PatentLaid-Open Publication No. 2011-122236 Patent Document 2: Japanese PatentLaid-Open Publication No. 2009-289587 Patent Document 3: InternationalPatent Laid-Open Publication No. 2009/008393 Patent Document 4:International Patent Laid-Open Publication No. 2009/008390 DISCLOSURE OFTHE INVENTION Problems to be Solved by the Invention

In view of the situation mentioned above, problems to be solved by thepresent invention are to provide a gold-nickel alloy nanoparticle thatcan fully express the afore-mentioned characteristics as the gold-nickelalloy nanoparticle and to provide a method for producing the same.

Means for Solving the Problems

The present invention solves the problem as mentioned above by providinga solid gold-nickel alloy nanoparticle and a method for producing thesame.

The present invention may be executed as an embodiment of a solidgold-nickel alloy nanoparticle wherein as a result of microrangeanalysis of the solid gold-nickel alloy nanoparticle by a TEM-EDSanalysis using a beam diameter of 5 nm, molar ratios of gold and nickelin 50% or more of analysis points thereof are detected within ±30% ofmolar ratios of gold and nickel obtained by ICP analysis result of thesolid gold-nickel alloy nanoparticle.

In addition, the present invention may be executed as an embodiment of asolid gold-nickel alloy nanoparticle wherein as a result of microrangeanalysis of the solid gold-nickel alloy nanoparticle by a STEM-EDSanalysis using a beam diameter of 0.2 nm, molar ratios of gold andnickel in 50% or more of analysis points thereof are detected within±30% of molar ratios of gold and nickel obtained by ICP analysis resultof the solid gold-nickel alloy nanoparticle.

Further, the present invention may be executed as an embodiment of asolid gold-nickel alloy nanoparticle wherein a nickel concentrationcontained in the gold-nickel alloy is in the range of 2.0 to 92.7% byweight, and the solid gold-nickel alloy nanoparticle comprises mainly agold-nickel alloy showing a finely mixed state of gold and nickel in ananometer level.

The gold-nickel alloy nanoparticle of the present invention shows afinely mixed state of gold and nickel in a nanometer level even in aparticular solid phase region showing a non-solid solution state in anequilibrium diagram thereof. Meanwhile, in this particular solid phaseregion showing the non-solid solution state, gold and nickel areeccentrically located; and in the gold-nickel alloy, it is a regionwhich includes a eutectic body of gold and nickel.

The region in which gold and nickel are eccentrically located is aregion in which in the entire of the gold-nickel alloy nanoparticle thecomposition ratio of gold and nickel to constitute the alloy isdifferent by more than ±30% from the composition ratio of gold andnickel to constitute the alloy within an extremely small area with thesize in the level of nanometers by microrange analysis. Morespecifically, as a result of microrange analysis by a TEM-EDS analysisusing a beam diameter of 5 nm or as a result of microrange analysis by aSTEM-EDS analysis using a beam diameter of 0.2 nm, in 50% or more ofanalysis points, the two metals are present in the mixed state thereofwith molar ratios of gold and nickel are detected over ±30% of molarratios of gold and nickel obtained by ICP analysis result of thegold-nickel alloy nanoparticle. Conventional alloys are in the state inwhich of the at least two metals to constitute the alloy, one metal isnot present in these regions, for example, as shown in FIG. 14 to FIG.17.

On the other hand, the gold-nickel alloy nanoparticle of the presentinvention shows that gold and nickel are present as a finely mixed statein the level of nanometers. In the gold-nickel alloy nanoparticle of thepresent invention, preferably, both gold and nickel are detected in therange of 2.0 to 92.7% by weight of concentration of nickel contained inthe gold-nickel alloy in all of the analysis points as a result of themicrorange analysis by the TEM-EDS analysis using a beam diameter of 5nm. In addition, in the gold-nickel alloy nanoparticle of the presentinvention, both gold and nickel are detected in the range of 2.0 to92.7% by weight of concentration of nickel contained in the gold-nickelalloy in all of the analysis points as a result the microrange analysisby the STEM-EDS analysis using a beam diameter of 0.2 nm.

In the technology level today, accurate judgment whether the obtainedgold-nickel alloy nanoparticle is a solid solution or not cannot be madewithout using the TED-EDS analysis or the STED-EDS analysis as mentionedabove. On top that, it is also important to confirm distribution of theelements of gold to nickel by mapping. Inventors of the presentinvention carried out an extensive investigation as to variousconditions including a fluid which contains metal ions to constitute thealloy and a fluid which contains a reducing agent by using the apparatusshown in Patent Document 4 with which only alloy particles similar tothose shown in FIG. 14 to FIG. 17 had been obtained; and a result of it,they could succeed to develop the alloy showing the finely mixed stateof gold to nickel in the level of nanometers.

As discussed above, the gold-nickel alloy nanoparticle thereof in thepresent invention can fully express the characteristics expected as thealloy because gold and nickel show the finely mixed state thereof in thelevel of nanometers.

In the gold-nickel alloy nanoparticle of the present invention, it isthought that the alloy comprises mainly non-eutectic body structure notcontaining eutectic body of gold and nickel.

In addition, it is thought that the gold-nickel alloy nanoparticle ofthe present invention comprises mainly a substitutional solid solutionof gold and nickel. As it is well known, a solid solution is classifiedroughly into an interstitial solid solution and a substitutional solidsolution; the gold-nickel alloy nanoparticle that is obtained by thepresent invention is recognized as the substitutional solid solution.The substitutional solid solution and the interstitial solid solutionmay be differentiated by observation with TEM and STEM, XRD measurement,thermal analysis, and the like, while observation with TEM and STEM isespecially effective. The substitutional solid solution is the solidsolution in which metal elements at the lattice point in the spacelattice are substituted by other elements. Because of this, in thesubstitutional solid solution, a lattice fringe can be clearly observedespecially by observation of the alloy with TEM or STEM; and because ofthe effect of strain of the crystal lattice caused by replacement of themetal element with other element at the lattice point, the latticefringe is observed as the surged fringe. On the other hand, in theinterstitial solid solution, other element enters into the space of thecrystal lattice, so that the alloy is observed by TEM or STEM in thestate different from that of the substitutional solid solution alloy.

In the present invention, the gold-nickel alloy nanoparticle may beproduced by mixing a gold ion, a nickel ion, and a substance having areducing property in a thin film fluid formed between at least twoprocessing surfaces which are disposed in a position they are faced witheach other so as to be able to approach to and separate from each other,at least one of which rotates relative to the other, whereby separatingthe gold-nickel alloy nanoparticle. Specifically, it may be produced byusing the apparatus shown in Patent Documents 3 and 4.

The substance having a reducing property of the present invention may beat least two substances each having a reducing property.

Furthermore, in the present invention, the said at least two reducingsubstances each having a reducing property may be at least one substanceselected from the group consisting of a reducing agent, a dispersantshowing a reducing property, and a solvent showing a reducing property;and hydrazine monohydrate may be exemplified as the above-mentionedreducing agent.

In this apparatus, inventors of the present invention assume thatbecause the reducing reaction of gold to nickel could be controlled inthe atomic level, a homogenous mixing state of the gold-nickel alloycould be realized in the atomic level by controlling various conditionsincluding kinds of the processing fluids, pH thereof, mole ratio of thegold ion and the nickel ion, rotation number of the processing surfaces,and so forth.

The present invention may be executed as an embodiment wherein thegold-nickel alloy nanoparticle has a particle diameter of 500 nm orless, or further a particle diameter of 100 nm or less.

The present invention is a method for producing the gold-nickel alloynanoparticle, and may be executed as an embodiment, wherein a fluid tobe processed is supplied to between processing surfaces which relativelymoves so as to be able to approach to and separate from each other, adistance between the processing surfaces is kept in a minute space by abalance between a force toward an approaching direction and a forcetoward a separating direction, the forces including a supply pressure ofthe fluid to be processed and a pressure applied between the rotatingprocessing surfaces; by using this minute space kept between at leasttwo processing surfaces as a flow path of the fluid to be processed, thefluid to be processed forms a thin film fluid, and in this thin filmfluid the gold-nickel alloy microparticle is separated.

The present invention may be executed as an embodiment wherein at leasttwo fluids, a first fluid and a second fluid, are used as the fluids tobe processed, the first fluid contains a gold ion and a nickel ion, atleast any one of the first fluid and the second fluid contains asubstance having a reducing property, and the fluids to be processed aremixed in the thin film fluid.

Alternatively, the present invention may be executed as an embodimentwherein the substance having a reducing property is at least twosubstances each having a reducing property; and by using the at leasttwo substances each having a reducing property, gold and nickel areseparated out simultaneously. Namely, it is preferable that theseparation times of gold and nickel to constitute the gold-nickel alloynanoparticle be controlled such that they may be separatedsimultaneously whereby gold and nickel each may not be separated out asrespective single bodies; and therefore, by using at least twosubstances each having a reducing property, the separation times of goldand nickel each is controlled so that it becomes easy to separate outgold and nickel substantially at the same time; and as a result, thegold-nickel alloy nanoparticle showing the mixed state of gold andnickel in a nanometer level may be separated. As a matter of course,even when one substance having a reducing property is used, it ispossible to obtain the gold-nickel alloy nanoparticle showing the mixedstate of gold and nickel in a nanometer level.

Moreover, the present invention may be executed as an embodiment whereinthe at least two substances each having a reducing property is at leastone substance selected from the group consisting of a reducing agent, adispersant showing a reducing property, and a solvent showing a reducingproperty.

In the solid gold-nickel alloy nanoparticle of the present invention,gold and nickel in the gold-nickel alloy are substantially mixedtogether; and thus, performance as a high-reliable electric contactmaterial may be expressed, and in addition, characteristics expected asthe gold-nickel alloy, such as heat resistance, abrasion resistance,catalysis performance, and so forth may be fully expressed.

FIG. 1:

This shows a rough sectional view of the fluid processing apparatusaccording to the embodiment of the present invention.

FIG. 2:

This shows (A) a rough plane view of the first processing surface of thefluid processing apparatus shown in FIG. 1, and (B) an enlarged drawingof the essential part of the processing surface of the said apparatus.

FIG. 3:

This shows (A) a cross section view of the second introduction part ofthe said apparatus, and (B) an enlarged drawing of the essential part ofthe processing surface to explain the said second introduction part.

FIG. 4:

This shows an equilibrium diagram of Au—Ni alloy.

FIG. 5:

This shows the TEM picture of the gold-nickel alloy nanoparticleprepared in Example 1.

FIG. 6:

This shows the STEM picture of the gold-nickel alloy nanoparticleprepared in Example 2 and the STEM-EDS analysis points (4 points) in thegold-nickel alloy nanoparticle of the said STEM picture.

FIG. 7:

This shows the TEM picture of the gold-nickel alloy nanoparticleprepared in Example 3 and the TEM-EDS analysis points (5 points) in thegold-nickel alloy nanoparticle of the said TEM picture.

FIG. 8:

This shows the EDS analysis results measured at each of the STEM-EDSanalysis points shown in FIG. 6 of the gold-nickel alloy nanoparticleprepared in Example 2.

FIG. 9:

This shows the EDS analysis results measured at each of the TEM-EDSanalysis points, shown in FIG. 7, of the gold-nickel alloy nanoparticleprepared in Example 3.

FIG. 10:

This shows the low magnification TEM picture of the gold-nickel alloynanoparticle prepared in Example 1.

FIG. 11:

This shows (A) the STEM-HAADF picture, (B) the EDS mapping result (Au),and (C) the EDS mapping result (Ni) of the gold-nickel alloynanoparticle prepared in Example 5.

FIG. 12:

This shows (A) the STEM-HAADF picture (dark view) and (B) the STEM-BF(bright view) picture of the gold-nickel alloy nanoparticle prepared inExample 5 (magnification of 12 million in both (A) and (B)).

FIG. 13:

This shows (A) the STEM-HAADF picture (dark view) and (B) the STEM-BF(bright view) picture of the gold-nickel alloy nanoparticle prepared inExample 5 (magnification of 60 million in both (A) and (B)).

FIG. 14:

This shows (A) the STEM-HAADF picture, (B) the EELS mapping results(Ag), and (C) the EELS mapping results (Cu) of the observation resultswith an electron microscope which shows an example of a conventionalsilver-copper alloy particle.

FIG. 15:

This shows (A) the STEM-HAADF picture, (B) the STEM mapping results(Ag), and (C) the STEM mapping results (Cu) of the observation resultswith an electron microscope which shows other example of a conventionalsilver-copper alloy particle.

FIG. 16:

This shows (A) the STEM-HAADF picture, (B) the STEM mapping results(Ag), and (C) the STEM mapping results (Cu) of the observation resultswith an electron microscope which shows still other example of aconventional silver-copper alloy particle.

FIG. 17:

This shows (A) the STEM-HAADF picture, (B) the STEM mapping results(Ag), and (C) the STEM mapping results (Cu) and (Sb) of the observationresults with an electron microscope which shows other illustrativeexample of a conventional silver-antimony alloy particle.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereunder, one embodiment of the present invention will be specificallyexplained.

The gold-nickel alloy nanoparticle of the present invention shows afinely mixed state of gold and nickel in a nanometer level in aparticular solid phase region in which gold and nickel are eccentricallylocated in an equilibrium diagram of this alloy.

In the gold-nickel alloy, specific regions of the solid phase in whichthe gold and nickel are eccentrically located are shown in the alloyequilibrium diagrams, including the region which comprises mainly aeutectic body of the gold and nickel to constitute the alloy, and theregion which is an inhomogeneous solid solution even if the gold and thenickel form a solid solution.

Specifically, it is the α+β region in the equilibrium diagram of thegold-nickel alloy shown in FIG. 4. As it is well known, the state of analloy changes with temperature; and under a specific temperaturecondition of a solid having a specific composition ratio, gold andnickel are eccentrically located.

In the gold-nickel alloy, two metals are completely dissolved with eachother in a liquid phase, while they forma solid solution partially witheach other in a solid phase. Accordingly, the region shown as (α+β) inthe molar ratio (fraction) of the gold-nickel alloy is in the state inwhich the α phase and the β phase exist as two separated phases, so thatthis region is in the state in which the α phase and the β phase areeccentrically located in a very fine level.

On the other hand, in the gold-nickel alloy nanoparticle of the presentinvention, in the equilibrium diagram of the gold-nickel alloy shown inFIG. 4, gold and nickel to constitute the alloy shows a finely mixedstate in a nanometer level even in the α+β region.

Solid gold-nickel alloy nanoparticle, gold-nickel alloy showing finelymixed state of gold and nickel in the level of nanometers, and thenanoparticle thereof:

The solid gold-nickel alloy nanoparticle of the present invention is thegold-nickel alloy nanoparticle whose particle diameter is 500 nm orless, preferably the gold-nickel alloy nanoparticle whose particlediameter is 100 nm or less, or more preferably the gold-nickel alloynanoparticle whose particle diameter is 50 nm or less.

Further, the solid gold-nickel alloy nanoparticle of the presentinvention is a nanoparticle mainly comprising the gold-nickel alloy(AuNi alloy) which shows the finely mixed state of the gold and nickel,in the level of nanometers, wherein nickel concentration in thegold-nickel alloy is in the range of 2.0 to 92.7% by weight, orpreferably in the range of 3.0 to 90.0% by weight. A general Au—Ni alloyequilibrium diagram is shown in FIG. 4; generally, conventional alloyshave the mixed state of the α-phase and the β-phase. In the presentinvention, the gold-nickel alloy is homogeneous even in this region,whereby the gold-nickel alloy comprises mainly the alloy which is madeso as to show the finely mixed state of gold and nickel in the level ofnanometers. With this, not only performance as a high-reliable electriccontact material of electronic parts such as a connector, a small relay,and a printed wire board can be expressed, but also characteristicsexpected as the gold-nickel alloy, that is, heat resistance, abrasionresistance, catalysis performance, and so forth can be expressed. Asmentioned above, the gold-nickel alloy of the present invention is thegold-nickel alloy mainly comprising an alloy showing a finely mixedstate of gold and nickel in a nanometer level. In the present invention,“gold-nickel alloy mainly comprising an alloy showing a finely mixedstate of gold and nickel in a nanometer level” shall mean thegold-nickel alloy wherein 50% or more by volume of the gold-nickel alloyof the present invention is the alloy showing a finely mixed state ofgold and nickel in a nanometer level. Further, illustrative example ofthe alloy showing a finely mixed state of gold and nickel in a nanometerlevel in the present invention includes a solid solution and anamorphous thereof.

As mentioned above, inventors of the present invention observed thegold-nickel alloy nanoparticle of the present invention by means ofvarious instruments at room temperature, and determined that thegold-nickel alloy nanoparticle of the present invention was the solidgold-nickel alloy nanoparticle mainly comprising an alloy showing afinely mixed state of gold and nickel in a nanometer level.

More specifically, a gold-nickel alloy nanoparticle which was under thetemperature of room temperature was placed under the environment of themicroscopic analysis (TEM-EDS analysis or STEM-EDS analysis) used inExample as mentioned later and was exposed to an electron beam with anacceleration voltage of 200 kV; and under this condition, this wasconfirmed to be the gold-nickel alloy nanoparticle mainly comprising analloy showing a finely mixed state of gold and nickel in a nanometerlevel. During this observation, the temperature of the specimen itselfexposed to the electron beam was not controlled.

The analysis method as to the homogeneity of gold and nickel in thegold-nickel alloy and as to whether or not the gold-nickel alloy mainlycomprises the alloy which is made so as to show the finely mixed stateof gold and nickel in the level of nanometers is not particularlyrestricted, though a microscopic analysis method is preferable;especially for analysis in an extremely small area, an analysis methodby which the distribution state of gold and nickel as well as the weightratio or the mole ratio thereof can be analyzed is preferable.Illustrative example thereof includes the energy dispersive X-rayspectroscopy under observation with the transmission electron microscope(TEM-EDS), the energy dispersive X-ray spectroscopy under observationwith the scanning electron microscope (SEM-EDS), the high resolution TEM(HRTEM), the high-angle annular dark-field scanning transmissionelectron microscopy (HAADF-STEM), the element mapping method using thescanning transmission electron microscopy (STEM), the energy dispersiveX-ray spectroscopy under observation with the scanning transmissionelectron microscope (STEM-EDS), and the electron energy lossspectroscopy (EELS). Other methods may be used, too; but to demonstratethe homogeneity of gold and nickel in the gold-nickel alloy and whetheror not the gold-nickel alloy mainly comprises the alloy which is made soas to show the finely mixed state of gold and nickel in the level ofnanometers, a spectroscopic analysis is preferable. As to thegold-nickel alloy of the present invention which is the homogeneousgold-nickel alloy and comprises mainly the alloy which is made so as toshow the finely mixed state of gold and nickel in the level ofnanometers, the gold-nickel alloy nanoparticles shown by the TEMpictures and the STEM picture in FIG. 5, FIG. 6, and FIG. 7 andSTEM-HAADEF picture shown in FIG. 11 (FIG. 11 (A)) and the EDS mappingresult relating to these (FIG. 11 (B) and (C). Respectively (B) ismapping result of Au and (C) is mapping result of Ni) may beexemplified.

As to the gold-nickel alloy nanoparticles shown in FIG. 5, the ICPanalysis result of the gold-nickel alloy nanoparticle powders isAu:Ni=50.1:49.9 (mole ratio); in other words, the concentration ofnickel contained in the gold-nickel alloy is 22.9% by weight. As to thegold-nickel alloy nanoparticles shown in FIG. 6, the ICP analysis resultof the gold-nickel alloy nanoparticle powders is Au:Ni=14.9:85.1 (moleratio); in other words, the concentration of nickel contained in thegold-nickel alloy is 63.0% by weight. As to the gold-nickel alloynanoparticles shown in FIG. 7, the ICP analysis result of thegold-nickel alloy nanoparticle powders is Au:Ni=74.1:25.9 (mole ratio);in other words, the concentration of nickel contained in the gold-nickelalloy is 9.4% by weight. In the gold-nickel alloy nanoparticlesmentioned above, it was not confirmed that gold and nickel each wasclearly segregated in a single nanoparticle, even though all the ratiosof gold to nickel were in the α+β region in the Au—Ni alloy equilibriumdiagram; and in addition, the region of gold only or the region ofnickel only could not be confirmed. It is clear from the mapping resultshown in FIG. 11 (B) and (C). In FIG. 6, the STEM-EDS analysis points (4points) by using a beam diameter of 0.2 nm in the gold-nickel alloynanoparticle are shown; and in FIG. 8, the EDS analysis results obtainedby analyzing at respective analysis points shown in FIG. 6 are shown. Inthe gold-nickel alloy nanoparticle of the present invention, as theresult of the microregion analysis by the STEM-EDS analysis using thebeam diameter of 0.2 nm, in 50% or more of the analysis points, the moleratios of gold to nickel are detected preferably within ±30% of the moleratios of gold to nickel obtained by the ICP analysis result; and then,from the analysis results shown in FIG. 8, in 50% or more of theanalysis points, the mole ratios of gold to nickel by the STEM-EDSanalysis are detected within ±30% of the mole ratios of gold to nickelobtained by the ICP analysis result, and thus, this condition isfulfilled. The 0.2-nm beam is nearly equal to the atomic radius of goldand of nickel; however, in the actual observation, because informationsof the depth direction and of the surrounding area are taken, it ispossible to take informations substantially in the larger area than theatom size of gold and of nickel. If the gold-nickel alloy nanoparticleis inhomogeneous, or contains the portion in which was not made so as toshow the finely mixed state of gold and nickel in the level ofnanometers, then there should be many analysis points at which theratios of gold to nickel in the gold-nickel alloy nanoparticles are theratios of gold to nickel in α or β, respectively. And thus, it can beseen that the above-mentioned gold-nickel alloy nanoparticles are thehomogeneous gold-nickel alloy and are the gold-nickel alloy which ismade so as to show the finely mixed state of gold and nickel in thelevel of nanometers. Further, in FIG. 7, the TEM-EDS analysis points (5points) by using a beam diameter of 5 nm in the gold-nickel alloynanoparticle are shown; and in FIG. 9, the EDS analysis results obtainedby analyzing at respective analysis points shown in FIG. 7 are shown. Inthe gold-nickel alloy nanoparticles of the present invention, as theresult of analysis of the microregion analysis by the TEM-EDS analysisusing the beam diameter of 5 nm, in 50% or more of the analysis points,the mole ratios of gold to nickel are detected within ±30% of the moleratios of gold to nickel obtained by the ICP analysis result; and then,from the analysis results shown in FIG. 9, in 50% or more of theanalysis points, the mole ratios of gold to nickel by the TEM-EDSanalysis are detected within ±30% of the mole ratios of gold to nickelobtained by the ICP analysis result, and thus, this condition isfulfilled. In the present invention, the term “homogeneous gold-nickelalloy” means that this alloy is the gold-nickel alloy having theintended ratio of gold to nickel in the gold-nickel alloy; specifically,in a single gold-nickel alloy nanoparticle, the ratio of gold to nickel(mole ratio) obtained by the EDS analysis is within ±30% of the ratio ofgold to nickel (mole ratio) obtained by the ICP analysis result, whereinthe same results are obtained in plural gold-nickel alloy nanoparticles.And, the above-mentioned “homogeneous gold-nickel alloy” is thegold-nickel alloy in which gold and nickel are mixed homogeneouslytogether.

Analysis as described above in the present invention, it is preferableto be carried out in the range of diameter of 50 nm or less. In thepresent invention, the beam diameter of the EDS analysis (energydispersive X-ray spectrometric analysis) is different depending on thecapacity of the apparatus to be used; however, for example, it ispreferably 25 nm, more preferably 10 nm, or still more preferably 5 nm.In addition, depending on the analysis apparatus, it is more preferably0.5 nm, or still more preferably 0.2 nm. In the present invention,Examples were carried out by using the beam diameter of 5 nm in the caseof the TEM-EDS analysis; and the beam diameter of 0.2 nm was used in thecase of the STEM-EDS analysis. In addition, as the observation conditionof TEM or STEM, the magnifications of them are preferably 250,000 ormore, or more preferably 500,000 or more.

As to the EDS analysis method, determination of the analysis site is notparticularly restricted regardless of whether it is single site orplural sites; however, plural sites are preferable. In the case that theobject of the analysis is particle, the EDS analysis may be done as toeach of plural particles, or the EDS analysis may be done as to theplural sites of a single particle. For example, in the case that theparticle diameter is 5 nm and the EDS beam diameter is 5 nm, the EDSanalysis may be done as to plural particles, or the EDS analysis may bedone as to plural sites of a single particle by slightly changing theirradiation site of the beam in the EDS analysis. Alternatively, in thecase that the particle diameter is 5 nm and the EDS beam diameter is 0.2nm, the EDS analysis may be done as to plural sites of a singleparticle.

The number of the EDS analysis sites is not particularly restricted;however, it is preferably 3 sites or more, more preferably 10 sites ormore, or still more preferably 25 sites or more.

In the present invention, as the result of analysis of the gold-nickelalloy nanoparticle within the extremely small area by theafore-mentioned beam diameters using the TEM-EDS analysis or theSTEM-EDS analysis, in 50% or more, preferably in 65% or more, or morepreferably 80% or more of plural sites of the analysis points, the moleratios of gold to nickel are detected within ±30%, preferably within±20%, or more preferably within ±10% of the mole ratios of gold tonickel obtained by the ICP analysis result.

However, if the mole ratios exceed the range within ±30% of the moleratios of gold to nickel obtained by the ICP analysis result in 50% ormore of the analysis points, the mole ratios of gold to nickel in theanalysis results of the extremely small area obtained by the TEM-EDSanalysis or the STEM-EDS analysis are significantly different from themole ratios of gold to nickel obtained by the ICP analysis result; andthus, there is a possibility that the uniform gold-nickel alloynanoparticles may not be obtained.

There is no particular restriction as to the apparatus capable ofcarrying out the analyses as mentioned above. Illustrative examplethereof includes, as the apparatus capable of carrying out the analysisby the energy dispersive X-ray spectroscopy under observation with thetransmission electron microscope (TEM-EDS), the transmission electronmicroscope JEM-2100 (manufactured by JEOL Ltd.) equipped with the energydispersive X-ray analyzer JED-2300 (manufactured by JEOL Ltd.); and asthe energy dispersive X-ray spectroscopy under observation with thescanning transmission electron microscope (STEM-EDS), the highresolution transmission electron microscope Titan 80-300 (manufacturedby FEI Company) equipped with the r-TEM EDS detector (manufactured byAMETEK, Inc.), and the atomic resolution analytical electron microscopeJEM-ARM 200F (UHR) (manufactured by JEOL Ltd.) equipped with the energydispersive X-ray analyzer Centurio (manufactured by JEOL Ltd.).

Ratio of Gold to Nickel:

The ratio of gold to nickel (mole ratio) contained in the gold-nickelalloy nanoparticle of the present invention is not particularlyrestricted. Both the gold-nickel alloy having higher mole ratio of goldand the gold-nickel alloy having higher mole ratio of nickel may beused. Meanwhile, in the present invention, regardless of mole ratio ofgold to nickel contained in the gold-nickel alloy nanoparticle, all thealloys comprising gold and nickel are described as the gold-nickelalloy, and then the nanoparticle of gold-nickel alloy is described asthe gold-nickel alloy nanoparticle.

Nanoparticle Diameter of Gold-Nickel Alloy:

In the gold-nickel alloy nanoparticle of the present invention, asmentioned above, the gold-nickel alloy nanoparticle having particlediameter of 500 nm or less is preferable. More preferable is thegold-nickel alloy nanoparticle having particle diameter of 100 nm orless; and still more preferable is the gold-nickel alloy nanoparticlehaving particle diameter of 50 nm or less. This is because the particlewhose particle size is in the order of nanometer shows unique physicalcharacteristics such as lowered melting point and lowered sinteringtemperature due to the quantum size effect thereof. For example, as theprogress of nanotechnology in recent years, as the material to form acircuit on a plastic substrate by the coating and burning process, anelectrically conductive paste and the like for formation of anelectronic circuit by using nanoparticles are wanted; and the uniquephysical characteristics mentioned above may satisfy such needs amongothers. In the gold-nickel alloys of the present invention includingthose gold-nickel alloys shown in respective drawings, the particlediameters thereof were 500 nm or less in the obtained gold-nickel alloy;and there existed even the gold-nickel alloy nanoparticles having theparticle diameters of 100 nm or less as well as 50 nm or less.

As is the case with many other alloys, the gold-nickel alloynanoparticle of the present invention may contain minute amount ofimpurities in a certain instance; and thus, in the present invention ofthe gold-nickel alloy nanoparticle may contain intentionally orunintentionally an element other than gold or nickel. The element thatcan be intentionally contained therein may be exemplified by tinelement. It is not particularly restricted to intentionally contain theelement, and thus all elements may be mentioned, while illustrativeexample thereof includes gold, palladium, nickel, chromium, manganese,vanadium, iron, molybdenum, tin, and cobalt. If other metals are thoughtto be contained therein unintentionally as impurities, the ratio thereofis, though not particularly restricted, preferably less than 0.05% byweight, more preferably less than 0.02% by weight, or still morepreferably less than 0.01%, relative to entirety of the gold-nickelalloy.

Production Method 1 of Gold-Nickel Alloy Nanoparticle: Overview

Method for producing the above-mentioned gold-nickel alloy nanoparticleis not particularly restricted. Any of the method involving pyrolysis ofa gold and a nickel compound and the method involving reduction of agold and a nickel ion may be used; however, the production method of thegold-nickel alloy nanoparticle in which a fluid which contains a goldion and a nickel ion is mixed with a fluid which contains a reducingagent thereby separating the gold-nickel alloy nanoparticle ispreferable. Alternatively, the production method of the gold-nickelalloy nanoparticle in which a fluid which contains a gold ion, a fluidwhich contains a nickel ion, and a fluid which contains a reducing agentare mixed to separate nanoparticles of the gold-nickel alloynanoparticle may also be used. As the fluid which contains the reducingagent, two fluids comprising a first reducing fluid which contains atleast one reducing agent and a second reducing fluid which contains atleast one reducing agent other than the reducing agent used in the firstreducing fluid may be used.

Production Method 2 of Gold-Nickel Alloy Nanoparticle: A Fluid whichContains a Gold Ion and a Nickel Ion, and a Fluid which Contains a GoldIon and a Fluid which Contains a Nickel Ion

The fluid which contains a gold ion and a nickel ion, or the fluid whichcontains a gold ion and the fluid which contains a nickel ion are notparticularly restricted; however, a solution containing a gold ion and anickel ion, or a solution containing a gold ion and a solutioncontaining a nickel ion are preferable. Illustrative example of themethod to prepare them includes a method in which metal single body suchas gold or nickel is dissolved in hydrochloric acid, nitric acid, aquaregia, or the like, and a method in which a gold or a nickel compound isdissolved in a solvent. In addition, the fluid which contains a gold ionand a nickel ion may be obtained by dissolving a gold single body and/ora gold compound and a nickel single body and/or a nickel compound in asolvent all at once, or the fluid which contains a gold ion and a nickelion may be obtained by mixing a gold solution obtained by dissolving agold single body and/or a gold compound in a solvent with a nickelsolution obtained by dissolving a nickel single body and/or a nickelcompound in a solvent.

Compounds:

There are no restrictions as to the gold compound or the nickelcompound; and illustrative example thereof includes gold or nickel inthe form of salts, oxides, nitrides, carbides, complexes, organic salts,organic complexes, and organic compounds. There are no restrictions asto the gold salt or the nickel salt; and illustrative example thereofincludes nitrate salts, nitrite salts, sulfate salts, sulfite salts,formate salts, acetate salts, phosphate salts, phosphite salts,phosphinate salts, chlorides, oxy salts, and acetyl acetonato salts.Illustrative example of the other compounds includes gold alkoxides andnickel alkoxides.

Solvents:

The fluid which contains a gold ion and a nickel ion, or the fluid whichcontains a gold ion and the fluid which contains a nickel ion may beprepared by mixing the gold single body and/or the gold compound and/orthe nickel single body and/or the nickel compound with a solvent, orpreferably by dissolving or molecular-dispersing these substances in asolvent. In addition, the gold single body and/or the gold compoundand/or the nickel single body and/or the nickel compound may be carriedout by selecting single body or plural bodies from them in accordancewith an intended purpose. As the solvent to dissolve the gold singlebody and/or the gold compound and/or the nickel single body and/or thenickel compound, water, an organic solvent, or a mixture of them may beexemplified.

Illustrative example of the water includes a tap water, an ion-exchangedwater, a purified water, a ultrapurified water, and a RO water; andillustrative example of the organic solvent includes an alcohol compoundsolvent, an amide compound solvent, a ketone compound solvent, an ethercompound solvent, an aromatic compound solvent, carbon disulfide, analiphatic compound solvent, a nitrile compound solvent, a sulfoxidcompound solvent, a halogen compound solvent, an ester compound solvent,an ionic liquid, a carboxylic acid compound, and a sulfonic acidcompound. These solvents each may be used solely or as a mixture of twoor more of them.

Alternatively, a basic substance or an acidic substance may be used bymixing it with or dissolving it into the forgoing solvents Illustrativeexample of the basic substance includes metal hydroxides such as sodiumhydroxide and potassium hydroxide, metal alkoxides such as sodiummethoxide and sodium isopropoxide, and amine compounds such astriethylamine, 2-diethylaminoethanol, and diethylamine. Illustrativeexample of the acidic substance includes inorganic acids such as aquaregia, hydrochloric acid, nitric acid, fuming nitric acid, sulfuricacid, and fuming sulfuric acid; and organic acids such as formic acid,acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid,trifluoroacetic acid, and trichloroacetic acid. These basic substancesor acidic substances may be respectively used solely or as a mixturewith the solvents mentioned before.

Detailed Explanation of Solvents:

To explain the solvents mentioned above in more detail, illustrativeexample of the alcohol compound solvent includes methanol, ethanol,isopropanol, n-propanol, 1-methoxy-2-propanol, a linear alcohol such asn-butanol; branched alcohols such as 2-butanol and tert-butanol;polyalcohols such as ethylene glycol and diethylene glycol; andpropylene glycol monomethyl ether. Illustrative example of the ketonecompound solvent includes acetone, methyl ethyl ketone, andcyclohexanone. Illustrative example of the ether compound solventincludes dimethyl ether, diethyl ether, and tetrahydrofurane.Illustrative example of the aromatic compound solvent includes benzene,toluene, xylene, nitrobenzene, chlorobenzene, and dichlorobenzene.Illustrative example of the aliphatic compound solvent includes hexane.Illustrative example of the nitrile compound solvent includesacetonitrile. Illustrative example of the sulfoxide compound solventincludes dimethyl sulfoxide, diethylsulfoxide, hexamethylenesulfoxide,and sulfolane. Illustrative example of the halogen compound solventincludes chloroform, dichloromethane, trichloroethylene, and iodoform.Illustrative example of the ester compound solvent includes ethylacetate, butyl acetate, methyl lactate, ethyl lactate, and2-(1-methoxyl)propyl acetate. Illustrative example of the ionic liquidincludes a salt between 1-butyl-3-methylimidazolium and PF6⁻(hexafluorophosphate ion). Illustrative example of the amide compoundsolvent includes N,N-dimethylformamide, 1-methyl-2-pyrrolidone,2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, epsilon-caprolactam,formamide, N-methylformamide, acetamide, N-methylacetamide,N,N-dimetnylacetamide, N-methylpropanamide, and hexamethylphosphorictriamide. Illustrative example of the carboxylic acid compound includes2,2-dichloropropionic acid and squaric acid. Illustrative example of thesulfonic acid compound includes methanesulfonic acid, p-toluenesulfonicacid, chlorosulfonic acid, and trifluoromethanesulfonic acid.

Reducing Agents:

Meanwhile, the reducing agents are somewhat different from the above, sothat the entirety thereof is shown below.

There is no particular restriction as to the reducing agent, so that anyreducing agents capable of reducing a gold ion and/or a nickel ion maybe used. Illustrative example thereof includes hydride reducing agentssuch as sodium borohydride and lithium borohydride; aldehydes such asformalin and acetaldehyde; sulfite salts; carboxylic acids and lactonessuch as formic acid, citric acid, oxalic acid, succinic acid, ascorbicacid; aliphatic monoalcohols such as methanol, ethanol, butanol,isopropyl alcohol, and octanol; alicyclic alcohol such as terpineol;aliphatic diols such as ethylene glycol, propylene glycol, diethyleneglycol, dipropylene glycol, triethylene glycol, and tetraethyleneglycol; polyalcohols such as glycerin and trimethylolpropane; polyetherssuch as polyethylene glycol and polypropylene glycol; alkanol aminessuch as diethanol amine and monoethanol amine; and hydroquinone,resorcinol, aminophenol, glucose, sodium citrate, hypochlorous acid orits salts, transition metal ions (such as titanium ion and iron ion),hydrazines, and amines such as triethylamine, triethanolamine,diethylamino ethanol, octylamune, and dimethylaminoborane; pyrrolidone(such as polyvinyl pyrrolidone, 1-vinylpyrrolidone, N-vinylpyrrolidone,and methylpyrrolidone).

Reducing Agents: Hydrazines

In the present invention, at least one reducing agent selected from theabove-mentioned reducing agents is used. If two or more reducing agentsselected from the above-mentioned reducing agents are used, it may bepossible to control the reducing rates of gold and nickel, or theseparating times of gold and nickel. It is preferable to use a hydrazineas the reducing agent. Illustrative example of the hydrazine includeshydrazine, hydrazine monohydrate, hydrazinium carbonate, hydraziniumsulfate, phenyl hydrazine, 1-methyl-1-phenylhydrazine, and 1,1-diphenylhydrazine hydrochloride salt.

By using two or more reducing agents, as mentioned above, it may bepossible to control the reducing rates of gold and nickel, or theseparating times of gold and nickel. The mechanism as to how it workscannot be particularly restricted; however, it is thought that if anattempt is made to reduce gold and nickel which have differentcharacteristics with each other, especially gold and nickel which havedifferent standard electrode potentials (Ni²⁺+2e

Ni: −0.228E°/V, and Au⁺+e

Au: +1.68 E°/V, or [AuCl₄]⁻+3e

Au+4Cl⁻:1.002 E°/V, or [AuCl₂]⁻+e

Au+2Cl⁻:1.154 E°/V), by a single reducing agent, nobler and more readilyreducible gold tends to be reduced and separated faster than nickelthereby tending to separate out as the gold single body and the nickelsingle body respectively, or as an inhomogeneous alloy; however, if twoor more reducing agents are used, facilitation of the rates of reductionand separation of nickel, or retardation of the rates of reduction andseparation of gold, or both of them may occur to give rise the effect tosimultaneous separation of gold and nickel.

As mentioned above, of these reducing agents one reducing agent may beused; however, it is advantageous if at least two reducing agentsselected from these reducing agents are used because a gold ion and anickel ion to constitute the alloy may be reduced almost simultaneously.

Among the above-mentioned reducing agents, monoalcohols (such asmethanol, ethanol, butanol, isopropyl alcohol, octanol, and terpineol),aliphatic diols (such as ethylene glycol, propylene glycol, diethyleneglycol, dipropylene glycol, triethylene glycol, and tetraethyleneglycol), and polyvalent alcohol (such as glycerin and trimethylolpropane) may be used also as an solvent; and thus, they may be usedtogether with other reducing agent. Further, among the above-mentionedreducing agents, pyrrolidones (polyvinyl pyrrolidone, 1-vinylpyrrolidone, N-vinyl pyrrolidone, and methyl pyrrolidone) as well asamines (especially octylamine) can act also as a dispersant; and thus,they may be used together with other reducing agent. As seen above, areducing agent may be used together with a substance having a reducingproperty while being able to play other role, so that the reduction maybe controlled so as to reduce a gold ion and a nickel ion almostsimultaneously. In this case, the substance having a reducing propertythat can act as a solvent or as a dispersant may be blended not only inthe fluid which contains a reducing agent but also in the fluid whichcontains a gold ion and a nickel ion, in the fluid which contains a goldion, or in the fluid which contains a nickel ion.

Fluid which Contains Reducing Agent:

The fluid which contains a reducing agent contains preferably reducingagent mentioned above; and in addition, the reducing agent is preferablyin the state of solution, or in the state of being dissolved ormolecular dispersed by mixing with a solvent. There is no particularrestriction as to the solvent. The solvents mentioned before may be usedin accordance with the purpose. The fluid which contains the reducingagent may include the states such as dispersion solution and slurrysolution at the time of execution thereof.

In addition, as the fluid which contains a reducing agent, as mentionedabove, a fluid which contains at least two reducing agents may be used,or alternatively, as a fluid containing the reducing agent, two fluidscomprising a first fluid which contains at least one reducing agent anda second fluid which contains at least one reducing agent that isdifferent from the reducing agent used in the first fluid may also beused.

As to pH: The Fluid which Contains Gold and Nickel Ions or the Fluidwhich Contains Gold Ion and the Fluid which Contains Nickel Ion, theFluid which Contains Reducing Agent, and the Fluid after Mixing

In the present invention, pH of each of the fluids is not particularlyrestricted. It can be arbitrarily changed in accordance with mole ratioof gold and nickel, particle diameter, crystallinity, and so force inthe intended gold-nickel alloy nanoparticle. For example, adjustment ofpH of the fluid which contains gold and nickel or the fluid whichcontains gold and the fluid which contains nickel, and the fluid whichcontains a reducing agent may be executed by adding the afore-mentionedacidic substance or basic substance to the respective fluids; or pH maybe changed by gold and nickel, compound of them, or the reducing agentto be used, or by the respective concentrations. Further, pH of thefluid after separation of the gold-nickel alloy nanoparticle, the saidfluid being obtained by mixing a fluid which contains a reducing agentwith a fluid which contains a gold ion and a nickel ion, or with a fluidwhich contains a gold ion and a fluid which contains a nickel ion, isnot particularly restricted.

Temperature:

There is no particular restriction as to the temperature of each of thefluids of the present invention. Similarly to pH of each fluid of thepresent invention, the respective temperatures can be arbitrarilychanged in accordance with mole ratio of gold and nickel, particlediameter, crystallinity, and so force in the intended gold-nickel alloynanoparticles.

Dispersant and so Forth:

In the present invention, various dispersing agents and surfactants maybe used in accordance with the object and the necessity. Though notparticularly restricted, various commercially available generalsurfactants and dispersing agents as well as a newly synthesizedsubstance may be used. Illustrative example thereof includes an anionicsurfactant, a cationic surfactant, a nonionic surfactant, as well as adispersing agent such as various kinds of polymers. These may be usedsingly or as a combination of two or more of them. Among thedispersants, some of them have a reducing property; and as the exampleof it, polyvinylpyrrolidone and n-octylamine may be mentioned.

The afore-mentioned surfactant and dispersant may be contained in thefluid which contains a gold ion and a nickel ion, in the fluid whichcontains a gold ion and in the fluid which contains a nickel ion, in thefluid which contains a reducing agent, or in both of these fluids.Alternatively, the afore-mentioned surfactant and dispersant may becontained in a third fluid which is different from the fluid whichcontains a gold ion and a nickel ion, the fluid which contains a goldion, the fluid which contains a nickel ion, and the fluid which containsa reducing agent. Especially in order to improve dispersibility, it ispreferable that the dispersant etc. be introduced in advance into atleast any one of the fluid which contains a reducing agent, the fluidwhich contains a gold ion and a nickel ion, the fluid which contains agold ion, and the fluid which contains a nickel ion.

Fluid Processing Apparatus:

In the present invention, it is preferable that the fluid which containsthe gold and nickel ions be mixed with the fluid which contains areducing agent in a thin film fluid formed between processing surfaceswhich are disposed in a position they are faced with each other so as tobe able to approach to and separate from each other, at least one ofwhich rotates relative to the other, whereby separating the gold-nickelalloy nanoparticles; and it is preferable that the mixing be carried outby using the fluid-processing apparatus described in Patent Document 3and 4 filed by the present applicant to separate the gold-nickel alloynanoparticles. Hereunder, embodiments of the fluid processing apparatuswill be explained by using the drawings.

In conventional production methods, there were tendencies to form a gowhich gold-nickel alloy nanoparticle contains a mixture of a eutecticbody of gold and nickel and a solid solution of gold and nickel;however, in the present invention, by using the fluid processingapparatus shown below and by obtaining the mixed state of the specificregion of the solid phase, it became possible to obtain the gold-nickelalloy nanoparticle mainly comprising the non-eutectic body structure notcontaining the eutectic body of gold and nickel which is made so as toshow the finely mixed state of gold and nickel in the level ofnanometers. Applicant of the present invention considers the reason forthis as following: because the reducing reactions of gold and nickelcould be controlled in an atomic level, gold and nickel could realize ahomogeneous mixing state thereof in an atomic level.

However, preparation of the gold-nickel alloy nanoparticle by the fluidprocessing apparatus discussed later represents one example, so that anymethod may be used provided that the reducing reactions of gold andnickel can be controlled in an atomic level.

Explanation of Fluid Processing Apparatus

The fluid processing apparatus shown in FIG. 1 to FIG. 3 is similar tothe apparatus described in Patent Document 3, with which a material tobe processed is processed between processing surfaces in processingmembers arranged so as to be able to approach to and separate from eachother, at least one of which rotates relative to the other; wherein, ofthe fluids to be processed, a first fluid to be processed, i.e., a firstfluid, is introduced into between the processing surfaces, and a secondfluid to be processed, i.e., a second fluid, is introduced into betweenthe processing surfaces from a separate path that is independent of theflow path introducing the afore-mentioned first fluid and has an openingleading to between the processing surfaces, whereby the first fluid andthe second fluid are mixed and stirred between the processing surfaces.Meanwhile, in FIG. 1, a reference character U indicates an upside and areference character S indicates a downside; however, up and down, frondand back and right and left shown therein indicate merely a relativepositional relationship and does not indicate an absolute position. InFIG. 2(A) and FIG. 3(B), reference character R indicates a rotationaldirection. In FIG. 3(C), reference character C indicates a direction ofcentrifugal force (a radial direction).

In this apparatus provided with processing surfaces arranged opposite toeach other so as to be able to approach to and separate from each other,at least one of which rotates relative to the other, at least two kindsof fluids to be processed are used as the fluid to be processed, whereinat least one fluid thereof contains at least one kind of material to beprocessed, a thin film fluid is formed by converging the respectivefluids between these processing surfaces, and the material to beprocessed is processed in this thin film fluid. With this apparatus, aplurality of fluids to be processed may be processed as mentioned above;but a single fluid to be processed may be processed as well.

This fluid processing apparatus is provided with two processing membersof a first processing member 10 and a second processing member 20arranged opposite to each other, wherein at least one of theseprocessing members rotates. The surfaces arranged opposite to each otherof the respective processing members 10 and 20 are made to be therespective processing surfaces. The first processing member 10 isprovided with a first processing surface 1 and the second processingmember 20 is provided with a second processing surface 2.

The processing surfaces 1 and 2 are connected to a flow path of thefluid to be processed and constitute part of the flow path of the fluidto be processed. Distance between these processing surfaces 1 and 2 canbe changed as appropriate; and thus, the distance thereof is controlledso as to form a minute space usually less than 1 mm, for example, in therange of about 0.1 μm to about 50 μm. With this, the fluid to beprocessed passing through between the processing surfaces 1 and 2becomes a forced thin film fluid forced by the processing surfaces 1 and2.

When a plurality of fluids to be processed are processed by using thisapparatus, the apparatus is connected to a flow path of the first fluidto be processed whereby forming part of the flow path of the first fluidto be processed; and part of the flow path of the second fluid to beprocessed other than the first fluid to be processed is formed. In thisapparatus, the two paths converge into one, and two fluids to beprocessed are mixed between the processing surfaces 1 and 2 so that thefluids may be processed by reaction and so on. It is noted here that theterm “process(ing)” includes not only the embodiment wherein a materialto be processed is reacted but also the embodiment wherein a material tobe processed is only mixed or dispersed without accompanying reaction.

To specifically explain, this apparatus is provided with a first holder11 for holding the first processing member 10, a second holder 21 forholding the second processing member 20, a surface-approaching pressureimparting mechanism, a rotation drive member, a first introduction partd1, a second introduction part d2, and a fluid pressure impartingmechanism p.

As shown in FIG. 2(A), in this embodiment, the first processing member10 is a circular body, or more specifically a disk with a ring form.Similarly, the second processing member 20 is a disk with a ring form. Amaterial of the processing members 10 and 20 is not only metal but alsocarbon, ceramics, sintered metal, abrasion-resistant steel, sapphire,other metal subjected to hardening treatment, and rigid materialsubjected to lining, coating, or plating. In the processing members 10and 20 of this embodiment, at least part of the first and the secondsurfaces 1 and 2 arranged opposite to each other is mirror-polished.

Roughness of this mirror polished surface is not particularly limited;but surface roughness Ra is preferably 0.01 μm to 1.0 μm, or morepreferably 0.03 μm to 0.3 μm.

At least one of the holders can rotate relative to the other holder by arotation drive mechanism such as an electric motor (not shown indrawings). A reference numeral 50 in FIG. 1 indicates a rotary shaft ofthe rotation drive mechanism; in this embodiment, the first holder 11attached to this rotary shaft 50 rotates, and thereby the firstprocessing member 10 attached to this first holder 11 rotates relativeto the second processing member 20. As a matter of course, the secondprocessing member 20 may be made to rotate, or the both may be made torotate. Further in this embodiment, the first and second holders 11 and21 may be fixed, while the first and second processing members 10 and 20may be made to rotate relative to the first and second holders 11 and21.

At least any one of the first processing member 10 and the secondprocessing member 20 is able to approach to and separate from at leastany other member, thereby the processing surfaces 1 and 2 are able toapproach to and separate from each other.

In this embodiment, the second processing member 20 approaches to andseparates from the first processing member 10, wherein the secondprocessing member 20 is accepted in an accepting part 41 arranged in thesecond holder 21 so as to be able to rise and set. However, as opposedto the above, the first processing member 10 may approach to andseparate from the second processing member 20, or both of the processingmembers 10 and 20 may approach to and separate from each other.

This accepting part 41 is a concave portion for mainly accepting thatside of the second processing member 20 opposite to the secondprocessing surface 2, and this concave portion is a groove being formedinto a circle, i.e., a ring when viewed in a plane. This accepting part41 accepts the second processing member 20 with sufficient clearance sothat the second processing member 20 may rotate. Meanwhile, the secondprocessing member 20 may be arranged so as to be movable only parallelto the axial direction; alternatively, the second processing member 20may be made movable, by making this clearance larger, relative to theaccepting part 41 so as to make the center line of the processing member20 inclined, namely unparallel, to the axial direction of the acceptingpart 41, or movable so as to deviate the center line of the processingmember 20 and the center line of the accepting part 41 toward the radiusdirection.

It is preferable that the second processing member 20 be accepted by afloating mechanism so as to be movable in the three dimensionaldirection, as described above.

The fluids to be processed are introduced into between the processingsurfaces 1 and 2 from the first introduction part d1 and the secondintroduction part d2 under the state that pressure is applied thereto bya fluid pressure imparting mechanism p consisting of various pumps,potential energy, and so on. In this embodiment, the first introductionpart d1 is a flow path arranged in the center of the circular secondholder 21, and one end thereof is introduced into between the processingsurfaces 1 and 2 from inside the circular processing members 10 and 20.Through the second introduction part d2, the second fluid to beprocessed for reaction to the first fluid to be processed is introducedinto between the processing surfaces 1 and 2. In this embodiment, thesecond introduction part d2 is a flow path arranged inside the secondprocessing member 20, and one end thereof is open at the secondprocessing surface 2. The first fluid to be processed which ispressurized with the fluid pressure imparting mechanism p is introducedfrom the first introduction part d1 to the space inside the processingmembers 10 and 20 so as to pass through between the first and secondprocessing surfaces 1 and 2 to outside the processing members 10 and 20.From the second introduction part d2, the second fluid to be processedwhich is pressurized with the fluid pressure imparting mechanism p isprovided into between the processing surfaces 1 and 2, whereat thisfluid is converged with the first fluid to be processed, and there,various fluid processing such as mixing, stirring, emulsification,dispersion, reaction, deposition, crystallization, and separation areeffected, and then the fluid thus processed is discharged from theprocessing surfaces 1 and 2 to outside the processing members 10 and 20.Meanwhile, an environment outside the processing members 10 and 20 maybe made negative pressure by a vacuum pump.

The surface-approaching pressure imparting mechanism mentioned abovesupplies the processing members with force exerting in the direction ofapproaching the first processing surface 1 and the second processingsurface 2 each other. In this embodiment, the surface-approachingpressure imparting mechanism is arranged in the second holder 21 andbiases the second processing member 20 toward the first processingmember 10.

The surface-approaching pressure imparting mechanism is a mechanism togenerate a force (hereinafter “surface-approaching pressure”) to pressthe first processing surface 1 of the first processing member 10 and thesecond processing surface 2 of the second processing member 20 in thedirection to make them approach to each other. By the balance betweenthis surface-approaching pressure and the force to separate theprocessing surfaces 1 and 2 from each other, i.e., the force such as thefluid pressure, a thin film fluid having minute thickness in a level ofnanometer or micrometer is generated. In other words, the distancebetween the processing surfaces 1 and 2 is kept in a predeterminedminute distance by the balance between these forces.

In the embodiment shown in FIG. 1, the surface-approaching pressureimparting mechanism is arranged between the accepting part 41 and thesecond processing member 20. Specifically, the surface-approachingpressure imparting mechanism is composed of a spring 43 to bias thesecond processing member 20 toward the first processing member 10 and abiasing-fluid introduction part 44 to introduce a biasing fluid such asair and oil, wherein the surface-approaching pressure is provided by thespring 43 and the fluid pressure of the biasing fluid. Thesurface-approaching pressure may be provided by any one of this spring43 and the fluid pressure of this biasing fluid; and other forces suchas magnetic force and gravitation may also be used. The secondprocessing member 20 recedes from the first processing member 10 therebymaking a minute space between the processing surfaces by separatingforce, caused by viscosity and the pressure of the fluid to be processedapplied by the fluid pressure imparting mechanism p, against the bias ofthis surface-approaching pressure imparting mechanism. By this balancebetween the surface-approaching pressure and the separating force asmentioned above, the first processing surface 1 and the secondprocessing surface 2 can be set with the precision of a micrometerlevel; and thus the minute space between the processing surfaces 1 and 2may be set. The separating force mentioned above includes fluid pressureand viscosity of the fluid to be processed, centrifugal force byrotation of the processing members, negative pressure when negativepressure is applied to the biasing-fluid introduction part 44, andspring force when the spring 43 works as a pulling spring. Thissurface-approaching pressure imparting mechanism may be arranged also inthe first processing member 10, in place of the second processing member20, or in both of the processing members.

To specifically explain the separation force, the second processingmember 20 has the second processing surface 2 and a separationcontrolling surface 23 which is positioned inside the processing surface2 (namely at the entering side of the fluid to be processed into betweenthe first and second processing surfaces 1 and 2) and next to the secondprocessing surface 2. In this embodiment, the separation controllingsurface 23 is an inclined plane, but may be a horizontal plane. Thepressure of the fluid to be processed acts to the separation controllingsurface 23 to generate force directing to separate the second processingmember 20 from the first processing member 10. Therefore, the secondprocessing surface 2 and the separation controlling surface 23constitute a pressure receiving surface to generate the separationforce.

In the example shown in FIG. 1, an approach controlling surface 24 isformed in the second processing member 20. This approach controllingsurface 24 is a plane opposite, in the axial direction, to theseparation controlling surface 23 (upper plane in FIG. 1) and, by actionof pressure applied to the fluid to be processed, generates force ofapproaching the second processing member 20 toward the first processingmember 10.

Meanwhile, the pressure of the fluid to be processed exerted on thesecond processing surface 2 and the separation controlling surface 23,i.e., the fluid pressure, is understood as force constituting an openingforce in a mechanical seal. The ratio (area ratio A1/A2) of a projectedarea A1 of the approach controlling surface 24 projected on a virtualplane perpendicular to the direction of approaching and separating theprocessing surfaces 1 and 2, that is, to the direction of rising andsetting of the second processing member 20 (axial direction in FIG. 1),to a total area A2 of the projected area of the second processingsurface 2 of the second processing member 20 and the separationcontrolling surface 23 projected on the virtual plane is called asbalance ratio K, which is important for control of the opening force.This opening force can be controlled by the pressure of the fluid to beprocessed, i.e., the fluid pressure, by changing the balance line, i.e.,by changing the area A1 of the approach controlling surface 24.

Sliding surface actual surface pressure P, i.e., the fluid pressure outof the surface-approaching pressures, is calculated according to thefollowing equation:

P=P1×(K−k)+Ps

Here, P1 represents the pressure of a fluid to be processed, i.e., thefluid pressure, K represents the balance ratio, k represents an openingforce coefficient, and Ps represents a spring and back pressure.

By controlling this balance line to control the sliding surface actualsurface pressure P, the space between the processing surfaces 1 and 2 isformed as a desired minute space, thereby forming a fluid film of thefluid to be processed so as to make the processed substance such as aproduct fine and to effect uniform processing by reaction.

Meanwhile, the approach controlling surface 24 may have a larger areathan the separation controlling surface 23, though this is not shown inthe drawing.

The fluid to be processed becomes a forced thin film fluid by theprocessing surfaces 1 and 2 that keep the minute space therebetween,whereby the fluid is forced to move out from the circular, processingsurfaces 1 and 2. However, the first processing member 10 is rotating;and thus, the mixed fluid to be processed does not move linearly frominside the circular, processing surfaces 1 and 2 to outside thereof, butdoes move spirally from the inside to the outside thereof by a resultantvector acting on the fluid to be processed, the vector being composed ofa moving vector toward the radius direction of the circle and a movingvector toward the circumferential direction.

Meanwhile, a rotary shaft 50 is not only limited to be placedvertically, but may also be placed horizontally, or at a slant. This isbecause the fluid to be processed is processed in a minute space betweenthe processing surfaces 1 and 2 so that the influence of gravity can besubstantially eliminated. In addition, this surface-approaching pressureimparting mechanism can function as a buffer mechanism ofmicro-vibration and rotation alignment by concurrent use of theforegoing floating mechanism with which the second processing member 20may be held displaceably.

In the first and second processing members 10 and 20, the temperaturethereof may be controlled by cooling or heating at least any one ofthem; in FIG. 1, an embodiment having temperature regulating mechanismsJ1 and J2 in the first and second processing members 10 and 20 is shown.Alternatively, the temperature may be regulated by cooling or heatingthe introducing fluid to be processed. These temperatures may be used toseparate the processed substance or may be set so as to generate Benardconvection or Marangoni convection in the fluid to be processed betweenthe first and second processing surfaces 1 and 2.

As shown in FIG. 2, in the first processing surface 1 of the firstprocessing member 10, a groove-like depression 13 extended toward anouter side from the central part of the first processing member 10,namely in a radius direction, may be formed. The depression 13 may be,as a plane view, curved or spirally extended on the first processingsurface 1 as shown in FIG. 2(B), or, though not shown in the drawing,may be extended straight radially, or bent at a right angle, or jogged;and the depression may be continuous, intermittent, or branched. Inaddition, this depression 13 may be formed also on the second processingsurface 2, or on both of the first and second processing surfaces 1 and2. By forming the depression 13 as mentioned above, the micro-pumpeffect can be obtained so that the fluid to be processed may be suckedinto between the first and second processing surfaces 10 and 20.

The base end of the depression 13 reaches preferably inner circumferenceof the first processing member 10. The front end of the depression 13extends in an outer circumferential direction of the first processingsurface 1 with the depth thereof (cross-sectional area) being graduallyshallower as going from the base end toward the front end.

Between the front end of the depression 13 and the outer periphery ofthe first processing surface 1 is arranged a flat surface 16 not havingthe depression 13.

When an opening d20 of the second introduction part d2 is arranged inthe second processing surface 2, the arrangement is done preferably at aposition opposite to the flat surface 16 of the first processing surface1 arranged at a position opposite thereto.

This opening d20 is arranged preferably in the downstream (outside inthis case) of the depression 13 of the first processing surface 1. Theopening is arranged especially preferably at a position opposite to theflat surface 16 located nearer to the outer diameter than a positionwhere the direction of flow upon introduction by the micro-pump effectis changed to the direction of a spiral and laminar flow formed betweenthe processing surfaces. Specifically, in FIG. 2(B), a distance n fromthe outermost side of the depression 13 arranged in the first processingsurface 1 in the radial direction is preferably about 0.5 mm or more.Especially in the case of separating microparticles from a fluid, it ispreferable that mixing of a plurality of fluids to be processed andseparation of the microparticles therefrom be effected under thecondition of a laminar flow. The shape of the opening part d20 may becircular as shown by solid lines in FIG. 2(B) and FIG. 3(B), or aconcentric circular ring of annular shape surrounding the opening in thecenter of the processing surface 2 having the ring disk shape as shownby dotted lines in FIG. 2(B).

If the opening part d20 having an annular shape is arranged so as to beconcentric circular ring surrounding the opening in the center of theprocessing surface 2, the second fluid to be introduced into between theprocessing surfaces 1 and 2 can be introduced to a wide range in thecircumferential direction with the same condition; and thus, the fluidprocessing, including diffusion, reaction, and separation, can be donemore uniformly. In order to produce large quantities of fine particles,the opening part d20 is preferably in the shape of annular shape, whileit is not necessary that the opening part d20 having an annular shape bearranged so as to be concentric circular ring surrounding the opening inthe center of the processing surface 2. If the opening part having theannular shape is used, the said opening part having the annular shapemay be continuous or discontinuous.

This second introduction part d2 may have directionality. For example,as shown in FIG. 3(A), the direction of introduction from the openingd20 of the second processing surface 2 is inclined at a predeterminedelevation angle (θ1) relative to the second processing surface 2. Theelevation angle (θ1) is set at more than 0° and less than 90°, and whenthe reaction speed is high, the angle (θ1) is preferably set in therange of 1° to 45°.

In addition, as shown in FIG. 3(B), introduction from the opening d20 ofthe second processing surface 2 has directionality in a plane along thesecond processing surface 2. The direction of introduction of thissecond fluid is in the outward direction departing from the center in aradial component of the processing surface and in the forward directionin a rotation component of the fluid between the rotating processingsurfaces. In other words, a predetermined angle (θ2) exists facing therotation direction R from a reference line g, which is the line to theoutward direction and in the radial direction passing through theopening d20. This angle (θ2) is also set preferably at more than 0° andless than 90°.

This angle (θ2) can vary depending on various conditions such as thetype of fluid, the reaction speed, viscosity, and the rotation speed ofthe processing surface. In addition, it is also possible not to give thedirectionality to the second introduction part d2 at all.

In the embodiment shown in FIG. 1, kinds of the fluid to be processedand numbers of the flow path thereof are set two respectively; but theymay be one, or three or more. In the embodiment shown in FIG. 1, thesecond fluid is introduced into between the processing surfaces 1 and 2from the introduction part d2; but this introduction part may bearranged in the first processing member 10 or in both. Alternatively, aplurality of introduction parts may be arranged relative to one fluid tobe processed. The opening for introduction arranged in each processingmember is not particularly restricted in its form, size, and number; andthese may be changed as appropriate. The opening of the introductionpart may be arranged just before the first and second processingsurfaces 1 and 2 or in the side of further upstream thereof.

To effect the reaction between the processing surfaces 1 and 2, thesecond fluid may be introduced through the first introduction part d1and the first fluid through the second introduction part d2, as opposedto the above description. That is, the expression “first” or “second”for each solvent has a meaning for merely discriminating an n^(th)solvent among a plurality of solvents present, and third or moresolvents can also be present.

In the above-mentioned apparatus, a treatment such asseparation/precipitation and crystallization is effected while beingmixed forcibly and uniformly between the processing surfaces 1 and 2which are disposed in a position they are faced with each other so as tobe able to approach to and separate from each other, at least one ofwhich rotates relative to the other, as shown in FIG. 1. Particlediameter and monodispersity of the treated substance to be processed canbe controlled by appropriately controlling rotation speed of theprocessing members 10 and 20, distance between the processing surfaces 1and 2, concentration of raw materials in the fluids to be processed,kind of solvents in the fluids to be processed, and so forth.

Hereunder, one example of specific embodiment of the production methodof the gold-nickel alloy nanoparticles by using the above-mentionedapparatus will be explained.

The separation reaction of the gold-nickel alloy nanoparticles takesplace while forcibly homogeneous mixing the fluids between theprocessing surfaces 1 and 2 which are disposed in a position they arefaced with each other so as to be able to approach to and separate fromeach other, at least one of which rotates relative to the other in theapparatus shown in FIG. 1 of the present application.

At first, a fluid which contains at least the gold ion and nickel ion isintroduced as the first fluid from the first introduction part d1, whichis one flow path, into between the processing surfaces 1 and 2 which aredisposed in a position they are faced with each other so as to be ableto approach to and separate from each other, at least one of whichrotates relative to the other, thereby forming between the processingsurfaces a first fluid film which is a thin film fluid formed of thefirst fluid.

Then, the fluid which contains a reducing agent is introduced as thesecond fluid into the first fluid film formed between the processingsurfaces 1 and 2 from the second introduction part d2 which is anotherflow path.

By so doing, the first fluid and the second fluid are mixed between theprocessing surfaces 1 and 2 while the distance therebetween is fixed bypressure balance between the supply pressure of the fluids to beprocessed and the pressure applied between the rotating processingsurfaces, thereby effecting the reaction to separate the gold-nickelalloy nanoparticle.

To effect the reaction between the processing surfaces 1 and 2, thesecond fluid may be introduced through the first introduction part d1and the first fluid through the second introduction part d2, as opposedto the above description. That is, the expression “first” or “second”for each solvent has a meaning for merely discriminating an n^(th)solvent among a plurality of solvents present, and third or moresolvents can also be present.

During the time of separating the gold-nickel alloy nanoparticles bycarrying out the reaction between the processing surfaces 1 and 2, thefirst fluid and the second fluid are controlled such that concentrationof nickel contained in the gold-nickel alloy nanoparticle may become2.0% or more by weight and less than 92.7% by weight.

During the time of separating the gold-nickel alloy nanoparticles bymixing a fluid which contains a gold ion and an nickel ion with a fluidwhich contains a reducing agent, respective concentrations in the fluidwhich contains the gold ion and the nickel ion in the fluid whichcontains the reducing agent are not particularly restricted; however,concentration of the gold ion in the fluid which contains the gold ionand the nickel ion is preferably in the range of 0.001 to 1.5000M(mol/L), concentration of the gold ion in the fluid which contains thegold ion and the nickel ion is preferably in the range of 0.0010 to1.5000 M (mol/L), and concentration of the reducing agent in the fluidwhich contains the reducing agent is preferably in the range of 0.0001to 25.000M (mol/L), though these are different depending on thecompounds to be used and the like.

By using the apparatus shown above, the gold-nickel alloy having finecrystalline particles with fewer lattice defects can be produced; andthus, it is also advantageous that the gold-nickel alloy nanoparticlesshowing the expected characteristics can be obtained.

Meanwhile, in observation by the electron microscope (TEM and STEM) ofrespective Examples of the present invention, clear lattice defects werenot confirmed.

It is thought that the homogeneous solid solution with the concentrationnot achievable before in the Gold-nickel alloy could be obtained becauseit is possible to mix and react them homogeneously in an atomic level byusing the apparatus discussed above.

As mentioned before, the processing apparatus may be provided with, inaddition to the first introduction part d1 and the second introductionpart d2, the third introduction part d3; and in this case, for example,each of the fluids which contains a gold ion as the first fluid, thefluid which contains an nickel ion as the second, and the fluid whichcontains a reducing agent as the third may be introduced into theapparatus. By so doing, concentration and pressure of each fluid can becontrolled separately so that the separation reaction of the gold-nickelalloy nanoparticles may be controlled more precisely. Similarly, theprocessing apparatus may be provided with, in addition to the firstintroduction part d1, the second introduction part d2, the thirdintroduction part d3, and in this case, for example, the fluid whichcontains a gold ion and an nickel ion as the first fluid, the firstreducing fluid which contains at least one reducing agent as the secondfluid, and the second reducing fluid which contains at least onereducing agent different from the reducing agent used in the firstreducing fluid as the third fluid may be respectively introduced intothe apparatus. Meanwhile, a combination of the fluids to be processed(first to third fluids) that are introduced into the respectiveintroduction parts may be set arbitrarily. The same is applied if theforth or more introduction parts are arranged; and by so doing, fluidsto be introduced into the processing apparatus may be subdivided. Inthis case, it is preferable that the fluid which contains a gold ion andthe fluid which contains an nickel ion be joined together before joiningwith the fluid which contains a reducing agent; and it is alsopreferable that the first reducing fluid and the second reducing fluidbe joined together before joining with the fluid which contains a goldion and an nickel ion.

In addition, temperatures of the fluids to be processed such as thefirst fluid, the second fluid, and so on may be controlled; andtemperature difference among the first fluid, the second fluid, and soon (namely, temperature difference among each of the supplied fluids tobe processed) may be controlled either. To control temperature andtemperature difference of each of the supplied fluids to be processed, amechanism with which temperature of each of the fluids to be processedis measured (temperature of the fluid before introduction to theprocessing apparatus, or in more detail, just before introduction intobetween the processing surfaces 1 and 2) so that each of the fluids tobe processed that is introduced into between the processing surfaces 1and 2 may be heated or cooled may be installed.

Hereunder, the present invention will be explained more specifically.However, the present invention is not limited to them.

Meanwhile, in the following Examples, the term “from the center” means“from the first introduction part d1” of the processing apparatus shownin FIG. 1; the first fluid means the first fluid to be processed whichis introduced from the first introduction part d1; and the second fluidmeans the second fluid to be processed which is introduced from thesecond introduction part d2 of the processing apparatus shown in FIG. 1.

TEM-EDS Analysis:

The quantitative analyses of gold and nickel in the gold-nickel alloynanoparticles by TEM-EDS were carried out by the transmission electronmicroscope JEM-2100 (manufactured by JEOL Ltd.) equipped with the energydispersive X-ray analyzer JED-2300 (manufactured by JEOL Ltd.). Theanalysis was done by using the beam diameter of 5 nm to calculate themole ratio of gold to nickel in the gold-nickel alloy nanoparticles.Specifically, 5 analysis points shown in FIG. 7 were chosen in each of10 of the obtained gold-nickel alloy nanoparticle; and mole ratios ofgold to nickel at respective analysis points were calculated, from whichvalues the average value was used.

Specific conditions of the TEM observation and the TEM-EDS analysis wereas follows; a sample of the gold-nickel alloy nanoparticles was mountedon the transmission electron microscope at room temperature, and anelectron beam was irradiated to the sample of the gold-nickel alloynanoparticles with the acceleration voltage of 200 kV. During thisoperation, temperature of the sample was not controlled. By theobservations using a low acceleration voltage and the accelerationvoltage of 200 kV, it was confirmed that the electron beam irradiationdid not cause any changes in the gold-nickel alloy nanoparticles.

Meanwhile, the acceleration voltage of the electron beam to irradiatethe gold-nickel alloy nanoparticles can be set arbitrarily toapproximately several hundred kV by the used transmission electronmicroscope.

STEM-EDS Analysis:

The element mapping and the quantitative analyses of gold and nickel inthe gold-nickel alloy nanoparticles by STEM-EDS were carried out by theultra-high resolution transmission electron microscope TITAN 80-300(manufactured by FEI company) equipped with the γ-TEM EDS detector(manufactured by Ametek Inc.), and the atomic resolution analyticalelectron microscope JEM-ARM200F (UHR) (manufactured by JEOL Ltd.)equipped with the energy dispersive X-ray analyzer Centurio(manufactured by JEOL Ltd.). The analysis was done by using the beamdiameter of 0.2 nm to calculate the mole ratio of gold to nickel in thegold-nickel alloy nanoparticles. Specifically, 4 analysis points shownin FIG. 6 were chosen in each of 10 of the obtained gold-nickel alloynanoparticles; and mole ratios of gold to nickel at respective analysispoints were calculated, from which values the average value was used.

Specific conditions of the STEM observation, the TEM observation, andthe STEM-EDS analysis were as follows; a sample of the gold-nickel alloynanoparticles was mounted on the scanning transmission electronmicroscope at room temperature, and an electron beam was irradiated tothe sample of the gold-nickel alloy nanoparticles with the accelerationvoltage of 200 kV. During this operation, temperature of the sample wasnot controlled. By the observations using a low acceleration voltage andthe acceleration voltage of 200 kV, it was confirmed that the electronbeam irradiation did not cause any changes in the gold-nickel alloynanoparticles.

Meanwhile, the acceleration voltage of the electron beam to irradiatethe gold-nickel alloy nanoparticles can be set arbitrarily toapproximately several hundred kV by the used electron microscopes.

ICP Analysis:

Quantitative analyses of gold and nickel contained in the dried powdersof the gold-nickel alloy nanoparticles by the inductively coupled plasmaatomic emission spectrophotometry (ICP) were carried out by usingICPS-8100 (manufactured by Shimadzu Corp.).

As Examples 1 to 6, while the fluid which contained a gold ion and anickel ion was introduced as the first fluid from the center with thesupply pressure of 0.50 MPaG, the fluid which contained a reducing agentwas introduced as the second fluid into between the processing surfaces1 and 2 to mix the first fluid and the second fluid in the thin filmfluid formed therebetween. The respective supply temperatures of thefirst fluid and the second fluid were measured just before introductionof the first fluid and the second fluid into the processing apparatus(more specifically just before introduction into between the processingsurfaces 1 and 2). The dispersion solution of the gold-nickel alloynanoparticles was discharged from between the processing surfaces 1 and2. The discharged dispersion solution of the gold-nickel alloynanoparticles was treated by a centrifugal separator (20,000 G) to spindown the gold-nickel alloy nanoparticles. After the supernatant solutionthereof was removed, washing by methanol was repeated for three times;and then, the wet cake thus obtained was dried under air pressure at 25°C. to obtain dried powders of the gold-nickel alloy nanoparticles.Confirmation of the particle diameter of the gold-nickel alloynanoparticles was done by using the TEM observation; and judgmentthereof was done by the particle diameter of the primary particlethereof. The TEM measurements were done with the magnification of 50,000or more; and the minimum and maximum value of 3 spots were used. InTable 1, processing conditions of the first fluid are shown; and inTable 2, processing conditions of the second fluid are shown. In Table3, shown are rotation number of the processing surface 1, the ratio ofgold to nickel (mole ratio) obtained by the STEM-EDS analysis and theTEM-EDS analysis of the gold-nickel alloy nanoparticles, the ratio ofgold to nickel in the STEM-EDS analysis and the TEM-EDS analysis of thegold-nickel alloy nanoparticles, whether or not there was an analysispoint at which the ratio of gold to nickel was in α or β (in Table 3,this point is shown as measurement point), the ratio of gold to nickel(mole ratio) in the gold-nickel alloy nanoparticles by the ICP analysisresult which was done by using dried powders of the gold-nickel alloynanoparticles, and the nickel concentration (% by weight) contained inthe gold-nickel alloy. The abbreviations used in Table 1 and 2 and inTable 13 are as follows: EG; ethylene glycol, HAuCl₄.4H₂O; chloroauricacid tetrahydrate, NiCl₂.6H₂O; nickel chloride hexahydrate, HMH;hydrazine monohydrate, PVP; polyvinyl pyrrolidone, KOH; potassiumhydroxide, and PW; pure water.

As Comparative Examples 1 to 3, mixing of the first fluid and the secondfluid was carried out by using a beaker. Each of the same fluids whichcontained the gold ion and nickel ion as those of Examples 1 to 3 (inExample 3 and comparative Example 3, only the concentration of nickelchloride hexahydrate is different.) at 130° C. was added with stirringinto each of the same fluid which contained the reducing agent as thoseof Examples 1 to 3 at 20° C. in a beaker to mix them. The particlesrespectively obtained by the same procedures as those of Examples C1 toC3 were recovered; and they were subjected to the STEM-EDS analysis, theTEM-EDS analysis, and the ICP analysis.

From the results of the TEM-EDS analysis and the STEM-EDS analysis inall the analysis points, it was confirmed that the gold-nickel alloynanoparticles obtained in these Examples were the gold-nickel alloynanoparticles whose nickel concentrations contained in the gold-nickelalloy were in the range of 2.0 to 92.7% by weight (all were in the α+βregion of the Au—Ni alloy equilibrium diagram). In addition, there wasno analysis point detected at which the ratio of gold to nickel (moleratio) in the gold-nickel alloy nanoparticles obtained by these Exampleswas the ratio of gold to nickel (mole ratio) in α or β, respectively.

In FIG. 5, the TEM picture of the gold-nickel alloy nanoparticleobtained by Example 1 is shown; in FIG. 6, the STEM picture of thegold-nickel alloy nanoparticle obtained by Example 2 is shown; and inFIG. 7, the TEM picture of the gold-nickel alloy nanoparticle obtainedby Example 3 is shown. In FIG. 10, the TEM picture of the gold-nickelalloy nanoparticles obtained by Example 1 with a lower magnification isshown. As shown in FIG. 5 to FIG. 7, the clear state in which gold andnickel each is segregated was not confirmed in the gold-nickel alloynanoparticles obtained by these Examples.

In FIG. 11, the STEM-HAADF picture (A) and the EDS mapping results ofthe gold-nickel alloy nanoparticles obtained in Example 5 are shown((B); Au, and (C); Ni). In the analysis using the EDS mapping, a statesuch as the clear state in which gold and nickel were eccentricallyseparated in one particle was not found.

In addition, in FIG. 6, the gold-nickel alloy nanoparticle obtained inExample 2 by the STEM-EDS analysis points (4 points) by the particlediameter of 0.2 nm beam diameter, and in FIG. 8, the EDS analysis pointsmeasured at the each analysis point shown in FIG. 6 are shown. From theanalysis results shown in FIG. 8, in 50% or more of the analysis points,the mole ratios of gold to nickel in the STEM-EDS analysis were detectedwithin ±30% of the mole ratios of gold to nickel obtained by the ICPanalysis result.

The EDS analysis results in FIG. 8 are one example of the gold-nickelalloy nanoparticles obtained in Example 2; and in each of 10 gold-nickelalloy nanoparticles whose EDS analyses were conducted, in 50% or more ofthe analysis points, the mole ratios of gold to nickel in the STEM-EDSanalysis were detected within ±30% of the mole ratios of gold to nickelobtained by the ICP analysis result. In addition, as the results of thesimilar STEM-EDS analyses in other Examples shown in Table 3, theanalysis points at which the mole ratios of the gold to nickel in theSTEM-EDS analysis in some analysis points were maximum ±30% relative tothe mole ratios of gold to nickel obtained by the ICP analysis of eachExample were present.

In addition, in FIG. 7, the gold-nickel alloy nanoparticle obtained inExample 3 by the TEM-EDS analysis points (5 points) by the particlediameter of 5 nm beam diameter, and in FIG. 9, the EDS analysis resultmeasured at the each analysis point shown in FIG. 7 are shown. From theanalysis results shown in FIG. 9, in 50% or more of the analysis points,the mole ratios of gold to nickel, were detected within ±30% of the moleratios of gold to nickel obtained by the ICP analysis result.

The EDS analysis results in FIG. 9 are one example of the gold-nickelalloy nanoparticles obtained in Example 3; and in each of 10 gold-nickelalloy nanoparticles whose EDS analyses were conducted, in 50% or more ofthe analysis points, the mole ratios of gold to nickel in the TEM-EDSanalysis were detected within ±30% of the mole ratios of gold to nickelobtained by the ICP analysis result. In addition, as the results of thesimilar TEM-EDS analyses in other Examples shown in Table 3, theanalysis points at which the mole ratios of the gold to nickel in theTEM-EDS analysis in some analysis points were maximum ±30% relative tothe mole ratios of gold to nickel obtained by the ICP analysis of eachExample were present.

Next, in FIG. 12, the STEM pictures of the gold-nickel alloynanoparticles obtained in Example 5 with magnification of 12 million areshown ((A) the HAADF picture (dark field), and (B) the BF picture(bright field)). As shown in FIG. 12 (A) and (B), the surged latticefringes were observed in the gold-nickel alloy nanoparticles. In FIG.13, the STEM pictures of the gold-nickel alloy nanoparticles obtained inExample 5 with magnification of 60 million are shown ((A) the HAADFpicture (dark field), and (B) the BF picture (bright field)). In theSTEM pictures as shown in FIG. 13 (A) and (B), the surged latticefringes were confirmed in the gold-nickel alloy nanoparticles. In otherExamples with regard to the gold-nickel alloy nanoparticles (Examples 1to 4 and Example 6), the same lattice fringes were also confirmed.

In the case that each of gold and nickel forms the crystallite of itsown, there appear surges occasionally due to inconsistency in the grainboundary of these crystallites; however, the surges that were observedin the gold-nickel alloy nanoparticles of Example 5 were observed insidethe crystallite; and thus, it is thought that as gold and nickel formedthe solid solution, the surges were generated by strain of the crystallattice due to the difference of the atomic radius between them.

TABLE 1 First fluid Mixed and dissolved substance Supply pH Solvent 1 2temperature (pH test Example Kind (M) Kind (M) Kind (° C.) paper) 1 EG0.0075 HAuCl₄•4H₂O 0.0075 NiCl₂•6H₂O 130 2 to 3 2 EG 0.0017 HAuCl₄•4H₂O0.0096 NiCl₂•6H₂O 130 2 to 3 3 EG 0.0075 HAuCl₄•4H₂O 0.0026 NiCl₂•6H₂O130 2 to 3 4 EG 0.00024 HAuCl₄•4H₂O 0.00936 NiCl₂•6H₂O 130 2 to 3 5 EG0.0024 HAuCl₄•4H₂O 0.0008 NiCl₂•6H₂O 130 2 to 3 6 EG 0.0016 HAuCl₄•4H₂O0.0189 NiCl₂•6H₂O 130 2 to 3 Comparative EG 0.0075 HAuCl₄•4H₂O 0.0075NiCl₂•6H₂O 130 2 to 3 Example 1 Comparative EG 0.0017 HAuCl₄•4H₂O 0.0096NiCl₂•6H₂O 130 2 to 3 Example 2 Comparative EG 0.0075 HAuCl₄•4H₂O 0.0013NiCl₂•6H₂O 130 2 to 3 Example 3

TABLE 2 Second fluid Solvent Mixed and dissolved substance 2 2 3 SupplypH 1 (% by 1 (% by (% by temperature (pH test Example Kind weight) Name(M) Kind weight) Kind weight) Kind (° C.) paper) 1 EG 32.3 PW 2.15 HMH10.8 PVP 3.23 KOH 20 >14 2 EG 32.3 PW 2.15 HMH 10.8 PVP 3.23 KOH 20 >143 EG 32.3 PW 2.15 HMH 10.8 PVP 3.23 KOH 20 >14 4 EG 32.3 PW 2.15 HMH10.8 PVP 3.23 KOH 20 >14 5 EG 32.3 PW 2.15 HMH 10.8 PVP 3.23 KOH 20 >146 EG 32.3 PW 2.15 HMH 10.8 PVP 3.23 KOH 20 >14 Comparative EG 32.3 PW2.15 HMH 10.8 PVP 3.23 KOH 20 >14 Example 1 Comparative EG 32.3 PW 2.15HMH 10.8 PVP 3.23 KOH 20 >14 Example 2 Comparative EG 32.3 PW 2.15 HMH10.8 PVP 3.23 KOH 20 >14 Example 3

TABLE 3 EDS Processing Measurement Nickel surface point at whichconcentration Rotation STEM-EDS TEM-EDS the ratio of ICP contained inParticle number Gold Nickel Gold Nickel gold to nickel Gold Nickel AuNialloy diameter Example C (rpm) Mole ratio Mole ratio was in α or β Moleratio (% by weight) (nm) 1 1700 50.1 49.9 50.8 49.2 No 50.1 49.9 22.9 10to 20 2 1700 14.9 85.1 15.2 84.8 No 14.9 85.1 63.0  5 to 10 3 1700 74.325.7 75.0 25.0 No 74.1 25.9 9.4 30 to 50 4 1700 2.7 97.3 2.6 97.4 No 2.597.5 92.1 70 to 90 5 1700 75.3 24.7 73.9 26.1 No 75.4 24.6 8.9 150 to250 6 1700 7.7 92.3 7.6 92.4 No 7.8 92.2 77.9 480 Comparative 1700 12.387.7 46.9 53.1 Yes 50.1 49.9 22.9 250-740 Example 1 Comparative 1700 1.398.7 87.6 12.4 Yes 14.1 85.9 64.5 480 to 960 Example 2 Comparative 170099.9 0.1 4.6 95.4 Yes 83.6 16.4 5.5  320 to 1120 Example 3

From the above, in Examples 1 to 6, it was confirmed that thehomogeneous gold-nickel alloy nanoparticle which was made so as to showthe finely mixed state of gold and nickel in the level of nanometers,especially the substitutional solid solution alloy particle, could beobtained.

-   1 first processing surface-   2 second processing surface-   10 first processing member-   11 first holder-   20 second processing member-   21 second holder-   d1 first introduction part-   d2 second introduction part-   d20 opening

1. A gold-nickel alloy nanoparticle, which is a solid gold-nickel alloynanoparticle, wherein as a result of microrange analysis of the solidgold-nickel alloy nanoparticle by a TEM-EDS analysis using a beamdiameter of 5 nm, molar ratios of gold and of nickel in 50% or more ofanalysis points thereof are detected within ±30% of molar ratios of goldand nickel obtained by ICP analysis result of the solid gold-nickelalloy nanoparticle.
 2. A gold-nickel alloy nanoparticle, which is asolid gold-nickel alloy nanoparticle, wherein as a result of microrangeanalysis of the solid gold-nickel alloy nanoparticle by a STEM-EDSanalysis using a beam diameter of 0.2 nm, molar ratios of gold andnickel in 50% or more of analysis points thereof are detected within±30% of molar ratios of gold and nickel obtained by ICP analysis resultof the solid gold-nickel alloy nanoparticle.
 3. A gold-nickel alloynanoparticle, which is a solid gold-nickel alloy nanoparticle, wherein anickel concentration contained in the gold-nickel alloy is in the rangeof 2.0 to 92.7% by weight, and the solid gold-nickel alloy nanoparticlecomprises mainly a gold-nickel alloy showing a finely mixed state ofgold and nickel in a nanometer level.
 4. The gold-nickel alloynanoparticle according to claim 1, wherein the gold-nickel alloynanoparticle forms a solid solution.
 5. The gold-nickel alloynanoparticle according to claim 1, wherein the gold-nickel alloynanoparticle is separated by mixing a gold ion, a nickel ion, and asubstance having a reducing property in a thin film fluid formed betweenat least two processing surfaces which are disposed in a position facingeach other so as to be able to approach to and separate from each other,at least one of which rotates relative to the other.
 6. The gold-nickelalloy nanoparticle according to claim 5, wherein the substance having areducing property is at least two substances each having a reducingproperty.
 7. The gold-nickel alloy nanoparticle according to claim 1,wherein the gold-nickel alloy nanoparticle comprises mainly asubstitutional solid solution.
 8. The gold-nickel alloy nanoparticleaccording to claim 7, wherein the substitutional solid solution is theone in which a lattice fringe in a surged state is observed in acrystallite thereof in a TEM picture or a STEM picture.
 9. Thegold-nickel alloy nanoparticle according to claim 1, wherein both goldand nickel are detected in the range of 2.0 to 92.7% by weight ofconcentration of nickel contained in the gold-nickel alloy in all of theanalysis points as a result of the microrange analysis by the TEM-EDSanalysis using a beam diameter of 5 nm.
 10. The gold-nickel alloynanoparticle according to claim 1, wherein both gold and nickel aredetected in the range of 2.0 to 92.7% by weight of concentration ofnickel contained in the gold-nickel alloy in all of the analysis pointsas a result of the microrange analysis by the STEM-EDS analysis using abeam diameter of 0.2 nm.
 11. The gold-nickel alloy nanoparticleaccording to claim 1, wherein the gold-nickel alloy nanoparticle has aparticle diameter of 500 nm or less.
 12. The gold-nickel alloynanoparticle according to claim 1, wherein the gold-nickel alloynanoparticle has a particle diameter of 100 nm or less.
 13. Thegold-nickel alloy nanoparticle according to claim 6, wherein the atleast two substances each having a reducing property is at least onesubstance selected from the group consisting of a reducing agent, adispersant showing a reducing property, and a solvent showing a reducingproperty.
 14. A method for producing a gold-nickel alloy nanoparticle,which is the gold-nickel alloy nanoparticle according to claim 1, saidmethod comprising the step of: supplying a fluid to be processed tobetween processing surfaces which relatively moves so as to be able toapproach to and separate from each other; keeping a distance between theprocessing surfaces in a minute space by a balance between a forcetoward an approaching direction and a force toward a separationdirection, the forces including a supply pressure of the fluid to beprocessed and a pressure applied between the rotating processingsurfaces; by using this minute space kept between at least twoprocessing surfaces as a flow path of the fluid to be processed, formingthe fluid to be processed into a thin film fluid; and in this thin filmfluid, separating the gold-nickel alloy microparticle.
 15. The methodfor producing a gold-nickel alloy nanoparticle according to claim 14,further comprising the steps of: using at least two fluids, a firstfluid and a second fluid, as the fluids to be processed; the first fluidcontaining a gold ion and a nickel ion; at least any one of the firstfluid and the second fluid containing a substance having a reducingproperty; and missing the fluids to be processed in the thin film fluid.16. The method for producing a gold-nickel alloy nanoparticle accordingto claim 15, further comprising the steps of: the substance having areducing property is at least two substances each having a reducingproperty; and by using the at least two substances each having areducing property, separating out gold and nickel simultaneously. 17.The method for producing a gold-nickel alloy nanoparticle according toclaim 16, wherein the at least two reducing substances is at least onesubstance selected from the group consisting of a reducing agent, adispersant showing a reducing property, and a solvent showing a reducingproperty.
 18. The gold-nickel alloy nanoparticle according to claim 2,wherein the gold-nickel alloy nanoparticle forms a solid solution. 19.The gold-nickel alloy nanoparticle according to claim 3, wherein thegold-nickel alloy nanoparticle forms a solid solution.
 20. Thegold-nickel alloy nanoparticle according to claim 2, wherein thegold-nickel alloy nanoparticle is separated by mixing a gold ion, anickel ion, and a substance having a reducing property in a thin filmfluid formed between at least two processing surfaces which are disposedin a position facing each other so as to be able to approach to andseparate from each other, at least one of which rotates relative to theother.